Regional cerebral glucose utilization was measured, using positron emission tomography, in normal male volunteers at different ages. 18F-2-deoxy-D-glucose was injected intravenously, and brain radioactivity was scanned at different times thereafter. Subjects were screened for the absence of cardiovascular disease, or of secondary or primary brain disease. One normal volunteer was found in whom glucose utilization as well as regional cerebral blood flow, were reduced in the right parietal lobe in the absence of signs or symptoms. In addition, protocols were written for the application of positron emission tomography to subjects with Organic Dementia of the Alzheimer Type.